So, I finally found a truck and picked it up in Utah this weekend. It's a '93 W250 regular cab auto. It was pretty dirty when I got it but today I cleaned it up pretty good. Seems like it should be a pretty good one.

Couple questions:
- I was looking for the fuse box because the brake lights weren't working and I came across what I assume is the PCM behind the glove box. The thing is, it was unplugged.?? I thought the truck might need this to be working in order to shift but apparently not cuz it runs and shifts just fine. Why would this be unplugged?

- could the brake light switch be bad causing me to not have brake lights when the pedal is pushed but still deactivate the cruise when the pedal is pushed? I can get brake lights when I manually push the trailer brake control **** but not when the brake pedal is pushed.

 

The box behind the glovebox is for the abs. The PCM is under the hood. As for the fuse box, its behind the panel under the steering coumn.

 

check the brake light switch that the pedal arm pushes when the brake is released, sounds like it's bad... i think they are under $20 at an auto parts store. since the lights work with the brake controller you know it's not a fuse or the bulbs... that's where i would look. also make sure that the "tap" for the brake controller didn't sever the wire.

 

That makes more sense, I guess alot of rancher types unplug the ABS to make it easier to stop on dirt roads. I plugged it back in to see if it would fix the brake light situation but it didn't. I eventually found the fuse box yesterday and the fuse is good.

 

Yeah, I ordered the switch, it was 26 bucks at advance auto, I'll have it tomorrow about noon. I was certain that the switch was the only thing it could be until I tried the cruise control this afternoon. When you set the cruise and then tap the brake, the cruise disengages as it should. But if the switch was bad I would think the cruse would stay on. There's like 6 wires coming off that switch, don't know what they all go to. Can the brake light portion of the switch fail and not the cruise cancel portion????

 

Yes, any dual function switch can have one side work and the other not work, providing there are more than 2 wires.